Producing and using evaporative cooling chambers and clay pot coolers: BEST PRACTICES

These devices function according to a basic principle called "evaporative cooling," where the evaporation of water from a surface removes heat, creating a cooling effect. Evaporative cooling can improve vegetable storage shelf life by providing a stable storage environment with low temperature and high humidity, which reduces the rate of respiration and water loss and spoilage in most vegetables. The improved storage environment can have positive impacts, including reduced post-harvest losses, less time spent traveling to the market, monetary savings, and increased availability of vegetables for consumption. These devices can also have farther-reaching impacts, particularly on women, who often make pottery and could benefit economically from producing clay pots with local materials, as well as selling fruits and vegetables in more flexible markets that have access to evaporative cooling technology. Several hot and dry regions throughout the world could potentially benefit from evaporative cooling, including North Africa, the Sahel region of Africa, the Horn of Africa, southern Africa, the Middle East, arid regions of South Asia, and Australia. Evaporative cooling devices function on the principle of direct evaporative cooling, where heat is removed as water evaporates from the surface of the storage device. The evaporative cooling effect causes a decrease in temperature and an increase in the relative humidity inside the storage device, conditions that increase the shelf life of many vegetables. Water must be added at regular intervals to maintain the cooling effect. The watering frequency required can vary from several times a day to only a few times a week, depending on the storage device's material and design as well as the weather conditions. In hot and dry climates (greater than 25 °C and less than 40% humidity), ECCs and clay pot coolers can be expected to provide a storage environment with humidity greater than 80% and temperature at least 8 °C lower than the maximum daily ambient temperature. Evaporative cooling devices are not suitable for all contexts, and several factors should be assessed to determine if a device will meet user needs in a particular setting. Key considerations include operating conditions, such as low relative humidity (less than 40%), high temperature (daily maximum above 25 °C), access to water, and availability of locally available materials for construction. Additionally, the devices require regular maintenance, including watering and cleaning, to ensure optimal performance.